This invention can be incorporated as an improvement in the carbonator disclosed in co-pending U.S. patent application Ser. No. 799,911, filed Nov. 20, 1985, now abandoned in favor of application Ser. No. 07/257,128, filed Oct. 7, 1988, now abandoned in favor of application Ser. No. 07/511,941 which is admitted to be prior art to the invention. FIGS. 1-13 and the description thereof describe the admitted prior art.
The invention is directed to the long standing problem of maintaining the desired degree of carbonation in a carbonated liquid. For example, in post-mix dispensers, carbonated water is combined with a concentrate, such as syrup, to make a drink for the consumer. The carbonated water is produced in a pressurized vessel, typically called a carbonator, which generates a solution of water and dissolved gas (CO.sub.2). Due to the pressurization of the carbonator and the requirement that the fluid be delivered to the consumer at ambient conditions, some method of flow control must be used to provide a consumer-acceptable flow rate of the carbonated water upon dispensing. The problem in controlling the flow arises because the solution of water and dissolved gas, i.e., the carbonated water, is an unstable mixture. At standard temperatures and pressures, the carbon dioxide gas tends to come out of solution. This tendency is accelerated if the solution is exposed to any severe turbulent flow or sudden pressure drops. A similar problem arises in pre-mix dispensers where a mixture of carbonated water and syrup is dispensed.
Several solutions to the problem of controlling the flow rate of the carbonated liquid while maintaining the dissolved gas in solution have been attempted with unsatisfactory results. For instance, as described in more detail subsequently in FIGS. 1-13, an expansion chamber can be provided to attempt to prevent the loss of carbonation when dispensing. The expansion chamber itself is kept at a cold temperature and is a gradually enlarging chamber which permits a gradual expansion and lowering of pressure from the pressure inside the carbonated tank, typically approximately 50 psi, to atmospheric pressure at the point where the carbonated water is dispensed to form a drink. The expansion chamber was used in combination with a anti-surge valve which acted to reduce the pressure in the expansion chamber to a level which would allow dispensing upon initial opening of the dispensing valve without spitting or sputtering. The expansion chamber did not provide satisfactory results because the inside diameter of the expansion chamber was so large that the carbonated solution was not in containment and therefore too much space was available for gas which readily came out of solution.
Another solution that was attempted was provision of a standard orifice of approximately 0.052 inches in diameter having a land distance of approximately 0.032 inches as the primary flow control. This is shown in FIG. 13A. The orifice was mounted at the outlet of the expansion chamber thereby effectively eliminating the reduced pressure effect of the expansion chamber. The above-mentioned anti-surge valve also was eliminated. Although this arrangement produced better results than the expansion chamber, it also was unsatisfactory because a rapid pressure drop and turbulent flow conditions were produced which tended to drive the dissolved carbon dioxide out of the solution.